Process for the manufacture of benzylphosphonates

ABSTRACT

PROCESS FOR THE MANUFACTURE OF 4-HYDROXYBENZYLPHOSPHONIC ESTER BY REACTING ESTERS OF PHOSPHORIC ACID WITH 4-HYDROXYBENZYLAMINES IN THE PRESENCE OF A BASE. THE COMPOUNDS MANUFACTURED ACCORDING TO THE INVENTION ARE USED AS STABILIZERS.

ABSTRACT OF THE DISCLOSURE Process for the manufacture of 4-hydroxybenzylphosphonic esters by reacting esters of phosphoric acid with 4-hydroxybenzylamines in the presence of a base. The compounds manufactured according to the invention are used as stabilizers.

The present invention relates toa process for the manufacture of compounds of the Formula I I O R4 R:

wherein R and R denote a straight-chain or branched alkyl group, a cycloalkyl group or an aralkyl group, R and R independently of one another denote a straightchain or branched alkyl group, a cycloalkyl group, an alkylthioalkyl group, an alkyloxalalkyl group, a halogenoalkyl group, an alkenyl group, the phenyl group or an alkylphenyl group, or together denote the groups characterized in that 1 mol of a compound of the Formula II I Ra B2 wherein R and R 'halve the abovementioned meaning and R and R independently of one another denote a straight-chain or branched alkyl group or together, and with inclusion of the nitrogen atom, denote a saturated "United States Patent ihce 3,790,648 Patented Feb. 5, 1974 phosphite of the Formula IH which is employed is almost completely incorporated into the end product of the Formula I, whereas according to the previously known process a part of the trialkyl phosphite is lost in the form of the alkyl halide. The fact that the splitting ofr of an alkyl halide is avoided in the process according to the invention also signifies a technological advance inasmuch as alkyl halides, especially lower alkyl halides, have to be destroyed by combustion, where, because of the halogen content, expensive absorption installations are needed to avoid contaminating the atmosphere. Finally, the substituted benzyl halides required for the previously known manufacturing process are unstable compounds of poor stability on storage, whilst the starting products of the Formula II required for the process according to the invention are stable compounds which can be stored.

It is furthermore known to manufacture compounds of the Formula I by reaction of appropriately substituted benzyl alcohols with trialkyl phosphites or triaryl phosphites, whilst splitting oif alcohols or phenols, respectively. The benzyl alcohols required for this are however industrially more difiicult to obtain than the starting products of the Formula H required for the process according to the invention. In other respects, what has been stated above applies as regards the more advantageous use of dialkyl phosphites in accordance with the process of the invention.

Finally it is known to manufacture compounds of the Formula I by reaction of appropriately substituted benzyltrialkylammonium iodides with trialkyl phosphites in the sense of a modified Arbusow reaction. However, the manufacture of the benzyltrialkylammonium iodides requires a further process stage as compared to the starting products of the Formula II which can be used according to the invention. In other respects, this process suffers from the same disadvantages as the Arbusow reaction of benzyl halides with trialkyl phosphites, described above.

Further general advantages of the process according to the invention are the relatively low reaction temperatures and the short reaction times, which repress the undesired L formation of colored by-products. The dialkylamines split off during the reaction can easily be removed because of their volatility and can furthermore be trapped and reemployed for the manufacture of the starting products of the Formula II, which represents a further advantage in dustrially. Furthermore, the dialkyl phosphites used in the heterocyclic ring, are reacted with one mol of a compound 7 of the Formula HI E O R4 (III) wherein R and B, have the aboven entioned meaning in the presence of a base.

It is known to manufacture p-hydroxybenzylphosphonates by reaction of appropriately substituted benzyl halides with trialkyl phosphites in the sense of an Arbusow process according to the invention are substantially less volatile than the corresponding trialkyl phosphites hitherto used and therefore produce a distinctly less objectionable odor during the reaction.

'According to the invention, it is preferred to manufacture compounds of the Formula I in which R and R independently of one another denotea straight-chain or branched alkyl group with 1 to 8 carbon atoms or a cycloalkyl group with *6 to 8 carbon atoms and R and R independently of one another denote a straight-chain or branched alkyl group with 1-22 carbon atoms, a cycloalkyl group with 6-8 carbon atoms, the groups wherein the alkyl groups possess 1-18 carbon atoms, the phenyl group or an alkylphenyl group with 7-14 carbon atoms.

invention is economically advantageous 'since the dialkyl In the preferred embodiment of the process according to the invention, compounds of the Formula II are used in which R and R independently of one another denote a straight-chain or branched alkyl group with 1 to 5 carbon atoms or together, with inclusion of the nitrogen atom, form a hydrogenated heterocyclic S-membered or 6-membered ring.

It is particularly preferred, according to the invention, to manufacture compounds of the Formula I in which R; denotes methyl or branched alkyl with 3-4 carbon atoms, R; denotes branched alkyl with 3 or 4 carbon atoms and R and R denote straight-chain or branched alkyl groups with 1-18 carbon atoms. Compounds ofthe Formula II in which R and R denote methyl, ethyl, propyl or isopropyl or together denote the radical of piperidine or morpholine are particularly preferentially employed for the manufacture of the compounds of the Formula I.

The process according to the invention can be carried out in the absence or in the presence of a solvent. Preferably, no solvent is used.

If R R R R R and R represent alkyl groups, these can, within the framework of the limits which have been indicated, be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertbutyl, amyl, tert.arnyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tetradecyl, hexadecyl, octdecyl, eicosyl or docosyl. These groups may also be alkyl substituents if R and R denote alkylphenyl. If R and R are halogenoalkyl groups, then these are preferably chloroalkyl groups with 1-18 carbon atoms, such as, for example, 2-chloroethyl. R and R can also be cyclic alkyl groups with 6 to 8 carbon atoms. These can be, for example, cyclohexyl, cycloheptyl or cyclooctyl, and the preferred cyclic alkyl group is the l-methylcyclo- Preferred'temperature ranges are 60-120 C.

hexyl-(l) group. If R and R are aralkyl groups, these can be groups with 7-12 carbon atoms, such as benzyl or phenylethyl. If R and R with inclusion of the nitrogen atom, form a heterocyclic S-membered or 6-membered ring, then this can be, for example, the radical of morpholine or piperidine.

If R is alkylthioalkyl, it can be hexadecylthioethyl, dodecylthioethyl, hexylthioethyl, octadecylthiopropyl, dodecylthiopropyl or hexylthiopropyl. If R;., denotes alkyloxalalkyl, this can be octadecyloxyethyl or dodecyloxyethyl. R as alkenyl is, for example, allyl.

If solvents are used in the process according tov the invention, then these can be aromatic hydrocarbons such as benzene or toluene, higher-boiling ethers, such as dioxane or ethylene glycol dimethyl ether, or aliphatic hydrocarbons or hydrocarbon mixtures, such as ligroin. Bases in the process according to the invention are, for example, alkali amides such as LlNHg or NaNI-I alkali hydrides, such as NaH or Lil-I, alkali hydroxides, such as LiII-I, NaOH or KOH, alcoholates such as NaOCI-I NaOC H or Mg(OC H Alkali amides and alkali alcoholates are preferred.

Alkali compounds of the phosphites of the Formula 111 can also be employed as bases. Their manufacture is effected, for example, by adding an alkali metal such as sodium to a phosphite of the Formula III.

Examples of compounds of the Formula III are dimethyl phosphite, diethyl phosphite, dibutyl phosphite, dihexyl phosphite, di-Z-ethylhexyl phosphite,- dioctyl phospite, didodecyl phosphite, dihexadecyl phosphite, dioctadecyl phosphite, didocosyl phosphite, diphenyl phosphite I or di-p-octylphenyl phosphite.

The starting compounds of the Formula II canbe manufactured from the corresponding 2,6-dialkylphenol, formaldehyde and a secondary amine HNR R as described, for example, in Netherlands Pat. 6803498.

In the process according to the invention, the reactants of the Formulae II and III are advantageously employed in molar ratios. Optionally, one of the two reactants can be used in an excess of up to 20%. The-base is employed in amounts of 1-30 mol percent, preferably 5-10 mol percent, relative to one of the reactants ofcthe Formula II or III. 4

The temperature in the process according to the invention are not critical. They are only important with re- If, for example, the reaction is carried out at 100 C The reaction according to the invention is preferably carried out under nitrogen or a noble gas, at normal pressure or reduced presusre, such as, for example, 10- mm. Hg. The reaction according to the invention can be carried out, for example, by warming the Compounds 11 and III and the base, withoutsolvents, under reduced p ressure'until no further amine is evolved, or by adding the base 'to a solution of the Compound III and then adding the compound II, in the same solvent as the CompoundIH, at elevated temperature.

The compounds obtained in accordance with the process of the invention are outstandingly suitable for use as stabilizers against the thermo-oxidative and/or photo-induced degradation of monomeric and polymeric substances, especially for the stabilization of polypropylene, of polyethylene, of polyamides, of polyacetals or of copolymers of ethylene, propylene and a diene such as, for example, norbornadiene or dicyclopentadiene.

The invention is explained in more detail in the examples which follow:

'4 EX'A' MPLE I I)l CzHa0\ )0 /C s /P\ no CH N\ (121150 H CH8 C(CHa):

0 0CgH5 HQ- -orn OCzHa 2):

13.8 g. (0.1 mol) of diethyl-phosphite are initially introduced into 100ml. of toluene and 0.69 g. (0.03 mol) of metallic sodium is added. The temperature rises to 40 C. whilst the sodium dissolves. The solution is treated with 26.3 g. (0.1 mol) of (4-hydroxy-3,5-di-tert.butylbenzyl)-dimethylamine in ml. of toluene and the mixture is boiled for one hour under reflux, in the course of which gaseous dimethylamine is evolved. When the evolution of dimethylamine has ceased, the mixture is cooled, water is added and the toluene phase is washed until neutral and evaporated. The residue is recrystallized from ligroin. 26.8 g. (75%) of 4-hydroxy-3,5-di-tert. butylbenzyl-phosphonic acid diethyl ester of melting point 122 C. arethus obtained.

If in this example the diethyl phosphite is replaced by an equimolecular amount of a phosphorous acid diester of Table I below,-and otherwise the same procedure is followed, the 4-hydroxy-3,5-di-tert.butylbenzylphosphonic acid diesters having the physical properties indicated are obtained in similar yields.

. .TABLE I 4-hydroxy-3,5-di-tert.butylbenzylphosphonic acid diester Boiling point (OlOHzCHzO) PHO 13.8 g. (0.1 mol) of diethyl phosphite and 29.1g; (0.1 mol) of (4-hydroxy-3,5-di-tert.butyl-benzyl)-diethylamine are mixed and heated to 80 C. whilst passing a slight stream of nitrogen through the mixture. After adding 0.1 g. (0.0044 mol) of lithium amide the pressure is reduced to'15 mm. Hg by means of a water pump and the mixture is warmed to 100 C. The evolution of diethylamine can be recognized from the vigorous formation of bubbles. After one hour, 0.3 g. of glacial acetic acid and 50' ml. of ligroin are added. On cooling, 4-hydroxy-3,5-di-tert.butylbenzylphosphonic acid diethyl ester precipitates as a white crystalline substance. Melting point 122 C., yield 32 g. (90%). v

If, in this example, (4-hydroxy-3,S-di-tert.butylbenzyl)-diethylamine is replaced by an equimolecular amount of (3-tert.butyl-4-hfydroxy-S-methyl-benzyl)-diethylamine and the analogous procedure is followed, and various dialkyl phosphites are employed, the (3-tert.butyl- 4-hydroxy-5 methylbenzyl)-phosphonic acid dialkyl esters indicated in Table II are obtained in good yield.

C (CH )3 .a (')/o R3 H O OHa-P l R4 CH3 TABLE II 3-tert.butyl-thydroxy-Em-methylbenzyl-phosphonio acid dialkyl ester Boiling point Melting Dialkyl phosphite C. Mm. point, C.

(CH30)2PHO 102 (C2H50)2PHO 102 (C4Hv-CH-CH2O)2PHO 216 5 (CgHmOhPHO 69-71 EXAMPLE 3 C (CH8)8 0 E370 0 /CH P HO CHI-N CiaHzwO H CH3 2 OC1sHa HO CHaP is a1 ah 29.3 g. (0.05 mol) of dioctadecyl phosphite and 13.3 (0.05 mol) of (4-hydroxy-3,5-di-tert.-butyl-benzyl)-dimethylamine are mixed and heated to 60 C. whilst passing a slight stream of nitrogen through the mixture, whereupon a homogeneous melt is produced. After adding 0.3 g. (0.013 mol) of lithium amide, the pressure is reduced to 15 .mm. Hg by means of a water pump and the mixture is slowly warmed to 100 C., in the course of which the evolution of dimethylamine starts at 80 C. After one hour the mixture is cooled to 50 C. and 1.0 g. of glacial acetic acid is added. On cooling to room temperature, the melt solidifies. After recrystallization from acetone, 35 g. (90%) of 4-hydroxy-3,5-di- 0f the 4-hydroxy-3,5-di-tert.butylbenzy1-phosphonic acid diester.

EXAMPLE 4 C Qs 23.4 g. (0.1 mol) of diphenyl phosphite are initially introduced into 50 ml. of absolute toluene, the solution is cooled to 5 C. and 0.48 g. (0.02 mol) of sodium hydride is added. The mixture is heated to the boil and a solution of 26.3 g. (0.1 mol) of (4-hydroxy-3,5-di-tert. butyl)-dimethylamine in ml. of absolute toluene is added dropwise. Thereafter the mixture is further boiled until the evolution of dimethylamine ceases (approx. 4 hours). After cooling, the mixture is neutralized with a little glacial acetic acid, water is added and the toluene phase is washed until neutral and evaporated. The residue is recrystallized from hexane. 33 g. (73%) of 4- hydroxy-3,5-di-tert.butylbenzyl-phosphonic acid diphenyl ester of melting point C. are thus obtained.

If, in this example, the diphenyl phosphite is replaced by an equimolecular amount of di-tert.octylphenyl phosphite and otherwise the same procedure is followed, 4- hydroxy-3,5-di-tert.butylbenzyl-phosphonic acid di-(tert. octylphenyl) ester is obtained in good yield, after distilling off the solvent, as a glass of a slight yellow color.

13.8 g. (0.1 mol) of diethyl phosphite and 17.9 g. (0.1 mol) of (4-hydroxy-3,5-dimethylbenzyl)-dimethylamine are mixed and heated to 100 C. 0.4 g. (0.01 mol) of sodium methylate is added at this temperature and the pressure is then reduced to 15 mm. Hg. When the reaction has subsided, which requires approx. 1 hour, the mixture is cooled and neutralized with glacial acetic acid. The melt is digested with hexane, whereupon crystallization occurs. After recrystallization from hexane, 4- hydroxy-3,5-dimethylbenzylphosphonic acid diethyl ester is obtained in a yield of 80%. Melting point: 72 C.

If, in this example, the (4-hydroxy-3,5-dimethylbenzyl)-dimethylamine is replaced by an equimolecular 7 amount of (4hydroxy-3,S-diisopropylbenzyl)-dimethylamine and the analogous procedure is followed, 4-hydroxy-3,5-diisopropylbenzyl-phosphonic acid diethyl ester is obtained in a yield of 65%. The substance is liquid and 13.8 g. (0.1 mol) of diethyl phosphite and 30.5 g. of N-(4-hydroxy-3,5-di-tert.butyl-benzyl)-morpholine (melting point 93-94 C.) are mixed and heated to 100 C. under nitrogen. After adding 0.2 g. (0.005 mol) of sodium amide, the pressure is reduced to 15 mm. Hg by means of a water pump and the mixture is kept at 100 C. for 2 hours. When the reaction has subsided, the mixture is cooled and neutralized with a little glacial acetic acid. On treating the reaction mixture with warm ligroin, 4-hydroxy-3,5-di-tert.butyl-benzyl-phosphonie acid diethyl ester precipitates as crystals. Yield 28 g. (80%); melting point, after one recrystallization from ligroin: 122 C.

What is claimed is: I

1. Process for the manufacture of compounds of the Formula I ii OR -onionlor which comprises reacting 1 mol of a compound of the Formula II HQ-QCm-N wherein R and R have the'abovementioned meaning and R and R independently of one another denote a straight-chain or branched alkyl group or together, and with inclusion of the nitrogen atom, denote a saturated heterocyclic ring, with one mol of a compound of the Formula III wherein R and R have the abovementioned meaning, in the presence of a base selected from alkali amides, alkali hydrides, alkali hydroxides, alkali alcoholates, and alkali compounds of the phosphites of the Formula III.

2. Process according to claim 1, wherein in the Compound I, R and R denote a straight-chain or branched alkyl group or a cycloalkyl group and R and R inde: pendently of one another denote a straight-chain or branched alkyl group, a cycloalkyl group, an alkylthioalkyl group, an alkyloxalkyl group, an alkenyl group, the phenyl group or an alkylphenyl group or together denote the groups -omomor 3. Process according to claim 2, wherein lithium amide is used as the base.

4. Pnocess according to claim 2, wherein the sodium compound of the compound of the Formula III is used as the base.

5. Process according to claim 2, wherein the reaction takes place in the presence of 1 to 30 mol percent of a base.

6. Process according to claim 2, wherein in the com pound of the Formula I, R and R independently of one another denote a straight-chain or branched alkyl group with 1 to 8 carbon atoms or a cycloalkyl group with 6 to 8 carbon atoms and R and R independently of one another denote a straight-chain or branched alkyl group with 1-22 carbon atoms,a cycloalkyl group with 6-8 carbon atoms, the --(CH -Sall yl or (CH 0alkyl groups, wherein the alkyl groups contain 1-18 carbon atoms, the phenyl group or an alkylphenyl group with 7-14 carbon atoms.

7. Process according to claim 2, wherein in the compound of the Formula II, R and R independently of one another denote. alkylwith 1-5 carbon atoms or together and with inclusion of the nitrogen atom form a hydrogenated heterocyclic S-membered or fi-rnembered ring.

8. Process according to claim 6, wherein in the Formula I, R denotes methyl or branched alkyl with 3-4 carbon atoms, R denotes branched alkyl with 3 or 4 carbon atoms and R and R denote straight-chain or branched alkyl groups with 1-18 carbon atoms.

9. Process according to claim 7, wherein in the Formula 11, R and R denote methyl, ethyl, propyl or isopropyl or together denote the radical of piperidine or morpholine.

10. Process according to claim 7, wherein in the Formula 11, R and R denote methyl, ethyl, propyl or isopropyl or together denote the radical of piperidine.

References Cited 7 UNITED STATES PATENTS I 2,635,112 4/1953 Fields 260-970 ANTON H. SU'ITO, Primary Examiner 7 US. (:1. xn. I 260-451 P, 247.1, 293.9, 948, 950, 953 

